1. Field of the Invention
The present invention generally relates to compact, high frequency, inductive fast charge transformers that function as a charging port for electric vehicles. More particularly, the present invention relates to a transformer that combines the features of existing inductive charging systems, with immersion cooling methods to surpass thermal charging capacities in comparison to transformers using conventional thermal cooling techniques.
2. Discussion of the Prior Art
Inductive charging systems for use in charging batteries of electric vehicles and the like, utilize a charge port comprising a secondary winding and a core which function as a secondary transformer in the electric vehicle. A charge coupler or probe comprising a primary winding and a core function as a primary transformer when coupled to a power source. When the primary transformer, or charge probe is inserted into the charge port, a fast charge transformer is formed that can be used for charging electric vehicle batteries. The charging of electric vehicle batteries is performed at high frequency and charging rates, causing a great deal of heat dissipation and buildup within the housing of the transformer. Heat dissipation represents charging efficiency losses, which could be in the kilowatt range when operating the transformer at high charging rates. Keeping the transformer components cool during operation is required in order to maximize transformer performance and reliability.
Different approaches have been used to implement thermal management of inductive transformers. One approach has been to rely on heat conduction methods where heat from the secondary winding and core is swept across an air gap interface to on-board heat exchangers which are cooled by charge port fans. However, this approach has been found to be prohibitive due to the additional equipment required and the energy needed to power the equipment.
Another approach has been to interface the on-board vehicle cooling systems with the transformer. Although air or liquid from the vehicle cooling system may become available in some near-term electric vehicles, such provision cannot be universally guaranteed for all vehicles. Furthermore, at charge rates above 25 kW, the increase in size and power consumption of fans and air chillers becomes prohibitive.
Thus, the current technology that is available for cooling inductive charging transformers of the type used in charging electric vehicle batteries is inefficient. Therefore, it would be desirable to provide an improved transformer apparatus and method of cooling such transformers.